1. Field of the Invention
The invention relates to power saving mechanisms in wireless networks, and in particular, to power saving mechanism over a wireless network using energy efficient scheduling for portable devices.
2. Brief Description of the Related Technology
A wireless network may comprise a plurality of battery operated handheld devices including a mobile phone, an MP3 player, a personal multimedia player (PMP), a camcorder, a personal digital assistant (PDA), etc. In such a battery operated handheld device, it is paramount to conserve power. In ad hoc mode operations as shown in FIG. 3, an MP3 player is downloading audio/video (AV) data from a hard disk and a mobile phone is uploading data (pictures) onto a PMP.
The IEEE 802.15.3 standard provides techniques for extending the operation time of battery powered electronic devices that communicate over a wireless network. The standard provides three major techniques to enable the battery powered device to turn off for one or more time periods: device synchronized power save (DSPS) mode, piconet-synchronized power save (PSPS) mode, and asynchronous power save (APS) mode. In the piconet, which is a wireless ad hoc data communication system that allows a plurality of data devices to communicate with each other, the devices operate in one of four power management (PM) modes: ACTIVE mode, DSPS mode, PSPS mode, or APS mode.
PSPS mode allows the devices to sleep at intervals defined by a piconet coordinator. The device sends a request to the piconet coordinator. The piconet coordinator then selects beacons that will be the system wake beacons and indicates that the device will be set to PSPS mode. All the devices in PSPS mode are required to listen for the system wake beacons.
DSPS mode is designed to enable groups of devices to sleep for multiple superframes but still be able to wake up during the same superframe. The devices synchronize their sleep patterns by joining a DSPS set which specifies the interval between wake periods for the devices and the next time the devices will be awake. Besides allowing the devices to wake up and exchange traffic at the same time, the use of DSPS sets makes it easy for other devices in the piconet to determine exactly when a DSPS device will be available to receive traffic.
APS mode allows a device to conserve power for extended periods until the device chooses to listen for a beacon. The only responsibility of a device in APS mode is to communicate with the piconet coordinator before the end of its association timeout period (ATP) in order to preserve its membership in the piconet.
The piconet coordinator allocates asynchronous channel time allocations (CTAs) to a destination device that is in either PSPS mode or DSPS mode in the wake superframes for that device.
Regardless of the device's power management mode, every device in the piconet is allowed to power down during parts of the superframe when the device is not scheduled to transmit or receive data.
Thus, techniques exist today that allows electronic devices that access a wireless communication network to conserve as much battery power as possible.